The Tibetan Plateau (TP) is referred to as the "water tower" of Asia for being home to the headwaters of many major rivers in Asia. It can also strongly modulate the Asian climate through dynamic and thermal processes.
Previous studies have shown that TP snow in winter/spring can significantly influence the Asian monsoon at interannual to interdecadal time scales. TP snow increased after the late 1970s and decreased after the late 1990s, contributing to simultaneous East Asian summer rainfall changes. However, little attention has been paid to the possible mechanism of TP precipitation change at interdecadal time scales.
Recently, Assoc. Prof. ZHU Yali from the Institute of Atmospheric Physics, Chinese Academy of Sciences, has uncovered a tripole winter precipitation change pattern around the TP in the late 1990s. In this pattern, the precipitation decreased over eastern India-southern TP-southern China, and increased to the north and south of these regions.
Further dynamical diagnosis and numerical experiment results showed that tropical Pacific SST changes could induce strengthened Walker circulation over the Pacific, causing ascending motion anomalies over the Indo-Pacific region. The regional meridional–vertical circulation was thus modulated, leading to descending motion anomalies over eastern India-southern TP-southern China. Combined with the effect of the changes in the East Asian westerly jet stream, a tripole precipitation pattern was formed around the TP.
"But other factors can also influence TP precipitation change, and more investigation is needed," said Prof. ZHU. Against the background of global warming, the impact of high-latitude climate systems, such as the Arctic sea ice, as well as anthropogenic activity, on TP precipitation, requires further analysis.
Snow-covered mountains on the Tibetan Plateau (Image by LEI Yanbin)
Yali Zhu, 2022. A tripole winter precipitation change pattern around the Tibetan Plateau in the late 1990s. Atmospheric and Oceanic Science Letters, https://doi.org/10.1016/j.aosl.2022.100223.
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